This invention relates to the field of downhole packers in wells. More particularly, the present invention relates to metal to metal seals that removably seal the lower end of an annular space in a well such as between an inner tubing and an outer casing.
Downhole packers seal the annular space between a casing cemented in a well bore and the well tubing through which underground fluid is removed or other fluid is injected into the well.
In certain situations, such as in pumping treated wastewater down below an aquifer for environmentally safe disposal, it is essential that the wastewater pass through to the bottom of the well without leaking into the intermediate strata that would contaminate future water supplies. To ensure safe operation, an inner tube carrying the wastewater down is surrounded by an outer tube or well casing. A seal commonly referred to as a packer, seals the lower end of the annular space between the inner and outer tube close to the lower end of the inner tube. The annular space is then filled with fluid and pressurized. The pressure in the annular space is then monitored to detect any change in pressure, which would indicate a leak of fluid either into, or out of, the annular space. Since the environment to which the inner and outer tubes are exposed may be corrosive or may induce cracks from soil movement, temperature and pressure fluctuations and the like, it is imperative that any leakage be immediately known. It is useful to be able to release the seal and pull the inner tubing out for repair and reuse if possible. It is also useful to be able to introduce corrosion inhibiting fluid into the annular space. Resilient sealing surfaces have been used in the prior art, but they tend to deteriorate in the hostile environment encountered. Prior art sealing elements have been applied to the inner and outer surfaces of the tubing, but they tend to lack structural strength.